There's an online trail map of Diablo (with elevation contours etc.) here.

I go with my 9-year old nephew Ryan to climb Mt. Diablo (3,849'). We drive through Clayton and park at the end of Regency Drive. I mark the location on my GPS, and we set out up Back Creek trail, which goes along a dry creek up a very scenic valley, with oak, Coulter pine, and lots of poison oak. I've brought a camera but no film.

The trail becomes progressively steeper as it heads for a saddle. It's fairly hot, and I notice that Ryan is drinking water at an alarming rate. The pace slows. We reach the saddle, cross the fire road, and continue on Bald Ridge trail. Vegetation switches to manzanita and sagebrush. We stop for lunch: graham crackers, cherries, and my packet of Food Goo: tangerine, with double caffeine.

We round a bend and the summit is in clear view. We've ascended from 500' to about 2,800'. Ryan's getting tired and our water is low so we turn around. We reach the saddle and Ryan wants to avoid the steep switchbacks so we decide to descend Meridian Ridge Trail, a broad fire trail that seems to go in the right direction.

Unfortunately the road soon veers off in a radically wrong direction. We backtrack and locate a connector to Back Creek trail, but it looks very long. An unsigned but distinct trail heads down the ridge in exactly the right direction, so we take it. The trail goes through sagebrush, which becomes increasingly dense to the point where we can barely move and it's not clear if there's still a trail. No retreat is possible at this point. I make a left turn off the ridge, heading down the slope to Back Creek trail. Another hundred yards of extremely unpleasant bushwacking brings us to the trail. We both have lots of scratches on arms and legs, with a fair amount of blood flowing from mine.

My GPS indicates 2.25 miles to the car, unpleasantly long, but it seems to have malfunctioned because we actually reach the car in about a quarter mile. We have drinks in the front seat but they've been superheated by direct sunlight so we head to a Quickee Mart and consume large, cold beverages.

A bit more adventure than planned but a lot of fun. I'll bag the peak at some point.